Manufacturers have recently expressed an interest in optical trackballs. An optical trackball typically includes an optical trackpad that is positioned on the front surface of a handset, just below the display. An infrared light source located below the trackpad emits infrared light towards the trackpad, and when a user places his finger on the trackpad, a sensor detects this event. The sensor detects the user's finger by receiving infrared light that has been reflected off the user's finger. The handset also determines the direction of motion of the user's finger on the trackpad, and this action is translated into corresponding functions associated with the handset.
Today's trackpads present several advantages over mechanical trackballs: they do not protrude from the front surface of the handset and they are hardier components because of their lack of moving parts. Nonetheless, current trackpads are typically unable to detect rotational movement of a user's finger. If a user rotates his finger on such a trackpad, the handset typically mistakenly interprets this motion as distinct vertical and horizontal movements.
Another disadvantage with today's handsets—no matter whether they rely on mechanical or optical trackballs—is the number of buttons or keys that are positioned on them, particularly on the edges or perimeter of the housing of the mobile phone. As a result, a user may become overwhelmed with all the various ways to control the features associated with his mobile phone.